Surgical instrument with replaceable loading unit

ABSTRACT

A surgical stapling device has an elongated body and a removable loading unit and a securing structure for securing the loading unit onto the elongated body. Guiding ramps guide the movement of the loading unit as it is mounted onto the elongated body. A movable yoke secures the loading unit onto the elongated body. A sensor mechanism is engaged by the loading unit and moves with the securing structure. The locking structure has a first position for blocking movement of the sensor mechanism and preventing removal of the loading unit. The locking unit has a second position for allowing the loading unit to be removed from the device.

BACKGROUND

1. Technical Field

This application relates to a surgical stapling device for applyingstaples to tissue having a locking mechanism for securing a loading unitonto the surgical stapling device.

2. Background of Related Art

Surgical devices for applying surgical fasteners to tissue are wellknown. Endoscopic surgical devices for applying staples, clips or otherfasteners include a handle assembly for actuating the device, anendoscopic shaft and a tool assembly at the distal end of the endoscopicshaft. Certain of these devices are designed for use with replaceableloading units housing the staples or fasteners. For example, in using anendoscopic linear stapler, the user may select a loading unit withstaples of a selected size and arranged in one or more lines of stapleshaving a selected staple line length. After firing, the user may removethe loading unit, select another loading unit of the same or differentsize, and fire staples from the instrument again. Endoscopic surgicalstaplers having four lines of staples, arranged in pairs on either sideof a cut line, are known.

Loading units in the form of replaceable cartridges are known. Inaddition, loading units having a tool assembly, including a cartridge,anvil, drive assembly and knife are known. Such loading units have thebenefit of providing a new knife with each loading of the loading unit.

Although interfaces between the surgical stapling device endoscopicshaft and the loading unit are known, improvements in the ease ofloading and unloading of the loading unit are desired.

SUMMARY

In a first aspect of the present disclosure, a surgical instrumentcomprises a loading unit having a tool assembly, and an elongated body.The elongated body has a proximal end and a distal end. The distal endof the elongated body includes a securing structure for securing theloading unit onto the elongated body. The securing structure includes atleast one guiding ramp and a moveable yoke with a first and a secondposition. The loading unit is secured on the elongated body when theyoke is in the second position. The at least one guiding ramp isarranged to guide movement of the loading unit in a predetermineddirection toward engagement with the yoke, and the yoke is movabletoward the second position as the loading unit is moved in thepredetermined direction.

The loading unit has a projecting part for engaging the yoke and the atleast one guiding ramp defines an arcuate path. The securing structureincludes a ring defining a passage. Two guiding ramps are defined by thering and extend in the passage.

The guiding ramps are helical in shape and are disposed approximately180 degrees apart. Each of the at least one guiding ramp extends towardthe proximal end of the elongated body.

The ring is attached to the distal end of the elongated body and theyoke is movably mounted to the ring so that the yoke is locatedproximally of the ring. The yoke is preferably rotatably mounted to thering through an inter-engaging groove and ridge structure for allowingrotation.

The yoke has at least one protrusion for engagement by the projectingpart on the loading unit. Preferably, the yoke has a pair of protrusionsfor being positioned on either side of the projecting part. The pair ofprotrusions is disposed adjacent a proximal end of the guiding ramp whenthe yoke is in the first position and defines a receiving space for theprojecting part.

The securing structure has a ledge and the projecting part of theloading unit is proximal to the ledge when the yoke is in the secondposition so that the loading unit is secured onto the elongated body.

In a further aspect of the present disclosure, a surgical instrumentcomprises an elongated body having a proximal end, a distal end, and arod extending therethrough, and a loading unit removably mountable withthe distal end of the elongated body. The loading unit has a toolassembly. A sensor mechanism is arranged for engagement by the loadingunit and for movement with the loading unit upon mounting the loadingunit on the distal end of the elongated body. A handle assembly includesa locking structure having a first position for blocking movement of thesensor mechanism and a second position for allowing movement of thesensor mechanism so that the loading unit is removable from theelongated body when the sensor mechanism is in the second position.

The locking structure engages the rod when the locking structure is inthe second position. This prevents movement of the rod when the loadingunit is not mounted on the elongated body of the instrument. The lockingstructure has a plunger arranged to engage the rod. The rod has a notcharranged for engagement by the plunger. The locking structure includes abutton that is accessible by the user of the surgical instrument andwhich can be used to change the locking structure from the firstposition to the second position.

The sensor mechanism preferably includes a sensor tube which is attachedto a movable yoke at a distal end of the sensor tube. The movable yokeis arranged for engagement by and movement with the loading unit. Thesensor tube is attached to a release flange at a proximal end thereof.The locking structure includes a tang for blocking movement of therelease flange when the locking structure is in the first position. Therelease flange includes a cam surface for camming a plunger intoengagement with the rod.

In another aspect of the present disclosure, a method of mounting aloading unit onto a surgical instrument comprises providing a surgicalinstrument with a handle assembly and an elongated body, the elongatedbody having a guiding ramp terminating at a receiving space defined byrotatable securing structure, and providing a loading unit with a toolassembly. The loading unit is engaged with the guiding ramp on theelongated body of the surgical instrument. The loading unit is rotatedso that the loading unit follows the guiding ramp and engages thesecuring structure, and the loading unit is rotated into a securedposition with respect to the elongated body so that the securingstructure rotates with the loading unit. The securing structure islocked when the loading unit is in the secured position. Preferably, astructure is provided for releasing the securing structure.

In a further aspect, a method of removing a loading unit from a surgicalinstrument comprises providing a surgical instrument with a handleassembly and an elongated body, the elongated body defining movablesecuring structure, the handle assembly having a locking structure witha first position blocking movement of the securing structure and asecond position allowing movement of the securing structure. A loadingunit with a distal tool assembly and a proximal housing portion isprovided. The loading unit is secured on the elongated body by thesecuring structure. The locking structure Is moved from the firstposition to the second position, and the loading unit is removed fromthe surgical instrument.

The loading unit is removed by rotating the loading unit, the loadingunit interacting with the securing structure so that the securingstructure moves with the loading unit. The loading unit is moved byrotating the loading unit and the securing structure rotates therewith.

BRIEF DESCRIPTION OF DRAWINGS

Various preferred embodiments of the presently disclosed surgicalstapling device are described herein with reference to the drawings, inwhich:

FIG. 1 is a perspective view of a surgical stapling device in accordancewith an embodiment of the present disclosure;

FIG. 2 is a side elevation view of the surgical stapling device of FIG.1;

FIG. 3 is a top plan view of the surgical stapling device of FIGS. 1-2;

FIG. 4 is a partial exploded view of the handle assembly for thesurgical stapling device of FIGS. 1-3;

FIG. 5 is a partial cross-sectional view of the surgical stapling deviceof FIGS. 1-4;

FIG. 6 is a perspective view of the surgical stapling device of FIGS.1-5, showing the DLU separated from the device;

FIG. 7 is a partial, exploded perspective view of the DLU for thesurgical stapling device of FIGS. 1-6;

FIG. 8 is a partial perspective view of the anvil member of the surgicalstapling device of FIGS. 1-7;

FIG. 9 is a partial, exploded perspective view of the DLU for thesurgical stapling device of FIGS. 1-8;

FIG. 10 is an exploded, perspective view of the tip assembly for thesurgical stapling device of FIGS. 1-9;

FIG. 11 is a perspective view of the tip assembly for the surgicalstapling device of FIGS. 1-10;

FIG. 12 is a perspective view of the tip assembly for the surgicalstapling device of FIGS. 1-11;

FIG. 13 is a partial perspective view of the elongated body and tipassembly for the surgical stapling device of FIGS. 1-12;

FIG. 14 is a partial, cross-sectional view of the tip assembly and DLUfor the surgical stapling device of FIGS. 1-13;

FIG. 15 is a partial, cross-sectional view of the tip assembly and DLUfor the surgical stapling device of FIGS. 1-14;

FIG. 16 is a partial, perspective view of the surgical stapling deviceof FIGS. 1-15 showing the elongated body;

FIG. 17 is a partial, perspective view, with parts removed, of thesurgical stapling device of FIG. 16, showing the elongated body;

FIG. 18 is a partial perspective view, with parts removed, of thesurgical stapling device of FIGS. 1-17, showing the tip assembly;

FIG. 19 is a partial perspective view with parts removed of the surgicalstapling device of FIGS. 1-18, showing the locking structure;

FIG. 20 is a partial perspective view with parts removed of the surgicalstapling device of FIGS. 1-19, showing the locking structure;

FIG. 21 is a partial cross-sectional view with parts removed of thesurgical stapling device of FIGS. 1-20, showing the locking structure;

FIG. 22 is a partial perspective view with parts removed of the surgicalstapling device of FIGS. 1-21, showing the locking structure; and

FIG. 23 is a partial cross-sectional view with parts removed of thesurgical stapling device of FIGS. 1-22, showing the locking structure.

DETAILED DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the presently disclosed surgical staplingdevice will now be described in detail with reference to the drawings inwhich like reference numerals designate identical or correspondingelements in each of the several views.

In the description that follows, the term “proximal” will refer to theend of the stapling device which is closest to the operator, while theterm “distal” will refer to the end of the device which is furthest fromthe operator.

FIGS. 1-23 illustrate one preferred embodiment of the presentlydisclosed surgical stapling device shown generally as 10. Briefly,surgical stapling device 10 includes a handle assembly 12 and anelongated body 14. The length of elongated body 14 may vary to suit aparticular surgical procedure. The elongated body 14 defines alongitudinal axis for the device 10. A replaceable loading unit or DLU16 is releasably secured to a distal end of elongated body 14. Loadingunit 16 includes a proximal body portion 18, which forms an extension ofelongated body 14, a distal tool assembly 20 including a cartridgeassembly 22, and an anvil assembly 24. Tool assembly 20 is pivotablyconnected to body portion 18 about an axis substantially perpendicularto the longitudinal axis of elongated body 14. Cartridge assembly 22houses a plurality of staples. Anvil assembly 24 is movable in relationto cartridge assembly 22 between an open position spaced from cartridgeassembly 22 and an approximated or clamped position in juxtaposedalignment with cartridge assembly 24. The staples are housed incartridge assembly 22 to apply rows of staples in body tissue. Forexample, in the embodiment shown, the rows of staples are linear rows ofstaples which may have a length measuring from about 30 mm to about 60mm. Other staple configurations and lengths are envisioned.

Handle assembly 12 includes a stationary handle member 26, a movablehandle or trigger 28 and a barrel portion 30. A rotatable member 32 ispreferably rotatably mounted to the forward end of barrel portion 30 andsecured to elongated body 14 to facilitate rotation of elongated body 14in relation to handle assembly 12. An articulation lever 122 issupported on a distal portion of barrel portion 30 and is operable, in amanner to be described hereafter, to effect articulation of toolassembly 20 with respect to body portion 18 of loading unit 16. A pairof return knobs 36 are movably supported along barrel portion 30.

Referring to FIGS. 4-7, handle assembly 12 includes a housing 38, whichis preferably formed from plastic molded housing half-sections 38 a and38 b. Alternately, other materials may be used to form the housingincluding metals, e.g., stainless steel. Housing 38 forms stationaryhandle 26 and barrel portion 30 of handle assembly 12 (see FIG. 1).Movable handle 28 is rotatably supported between housing half-sections38 a and 38 b about a cylindrical member 40 which is received within anopening 41 in movable handle 28. A biasing member 42, which ispreferably a torsion spring, urges movable handle 28 away fromstationary handle 26 to a non-compressed position. Movable handle 28includes a pair of throughbores 46 dimensioned to receive a pivot member47. A pawl 48 is rotatably supported on pivot member 47 and is biased bya spring 50 towards actuation shaft 52.

Actuation shaft 52 is slidably supported between retracted and advancedpositions within barrel portion 30 of housing 38 and includes a distalend defining a recess 54 configured to rotatably receive the proximalend 56 of firing rod 58. A spring biased retract arm 57 is rotatablymounted between housing half-sections 38 a and 38 b and includes anextension 57 a. Extension 57 a is positioned within a slot 59 (FIG. 4)formed in actuation shaft 52 to urge actuation shaft 52 to a fullyretracted position. Actuation shaft 52 includes a toothed rack 60. Pawl48 has an engagement finger 62 which is biased by spring 50 towardstoothed rack 60 of actuation shaft 52. When movable handle 28 isactuated, i.e., is compressed towards stationary handle 26 against thebias of spring 42, engagement finger 62 of pawl 48 engages toothed rack60 of actuation shaft 52 to advance actuation shaft 52 and firing rod 58distally. Distal end of firing rod 58 engages proximal end of driveassembly 212 of the loading unit 16, when proximal end of loading unit16 is engaged with elongated body 14 of surgical stapling device 10.

The surgical stapling device includes a disposable loading unit or“DLU.” A loading unit having the desired staple size or sizes, and thedesired staple line length, is assembled with the device. The loadingunits can include a tool assembly that can articulate with respect tothe proximal body portion, or loading units that do not providearticulation. The loading units can include tool assemblies havinglinear rows of staples or other staple configurations. After firingstaples from a loading unit, the loading unit can be removed from thedevice and a new loading unit may be assembled with the device.

Referring to FIGS. 1 and 7-9, a loading unit with an articulating toolassembly is shown. Loading unit 16 includes a tool assembly 20, aproximal body portion 18 and a mounting assembly 202 (FIG. 10). Bodyportion 18 has a proximal end adapted to releasably engage the distalend of the elongated body 14 in the manner to be discussed in detailbelow. Mounting assembly 202 is pivotally secured to a distal end ofbody portion 18 and is fixedly secured to a proximal end of toolassembly 20. Pivotal movement of mounting assembly 202 pivots the toolassembly 20 so that a longitudinal axis of the tool assembly 20 isangled with respect to the longitudinal axis of the elongated body 14.Pivotal movement of mounting assembly 202 about an axis substantiallyperpendicular to the longitudinal axis of the elongated body 14 effectsarticulation of tool assembly 20 between a non-articulated position inwhich the longitudinal axis of tool assembly 20 is aligned with thelongitudinal axis of elongated body 14 and an articulated position inwhich the longitudinal axis of tool assembly 20 is disposed at an angleto the longitudinal axis of elongated body 14.

Referring to FIGS. 7-9, tool assembly 20 includes a cartridge assembly22 and an anvil assembly 24. Anvil assembly 20 includes an anvil portion28 having a plurality of staple deforming concavities 30 (FIG. 9) and acover plate 32 secured to a top surface of anvil portion 28. Cover plate32 and anvil portion 28 define a cavity 34 therebetween. Cover plate 32prevents pinching of tissue during actuation of loading unit 16 andadvancement of the drive assembly 212 through the loading unit 16. Alongitudinal slot 38 extends through anvil portion 28 to facilitatepassage of a retention flange 40 of drive assembly 212. A cammingsurface 42 formed on anvil portion 28 is positioned to be engaged by apair of cam members 40 a supported on retention flange 40 of driveassembly 212 to effect approximation of the anvil and cartridgeassemblies. A pair of pivot members 211 and a pair of stabilizationmembers 215 are formed on the anvil portion 28.

Cartridge assembly 22 includes carrier 216 which defines an elongatedsupport channel 218 which is dimensioned and configured to receivestaple cartridge 220. Carrier 216 has a pair of shoulders 217 and a pairof slots 213 defined in the carrier 216. The pair of slots 213 receivesthe pair of pivot members 211 to allow the anvil portion 28 to pivotwith respect to the cartridge assembly 22. Each of the pair ofstabilization members 215 engages a respective shoulder 217 to preventthe anvil portion 28 from sliding axially in relation to the staplecartridge 220 as the anvil portion 28 is pivoted about the pivot members211. Corresponding tabs 222 and slots 224 formed along staple cartridge220 and elongated support channel 218, respectively, function to retainstaple cartridge 220 at a fixed location within support channel 218. Apair of support struts 223 formed on staple cartridge 220 are positionedto rest on side walls of carrier 216 to further stabilize staplecartridge 220 within support channel 218.

Staple cartridge 220 includes retention slots 225 (FIG. 7) for receivinga plurality of staples or fasteners 226 and pushers 228. A plurality oflaterally spaced apart longitudinal slots 230 extend through staplecartridge 220 to accommodate upstanding cam wedges 232 of an actuationsled 234 (FIG. 7). A central longitudinal slot 282 extends alongsubstantially the length of staple cartridge 220 to facilitate passageof the drive assembly 212 (FIG. 9). During operation of surgicalstapling device 10, drive assembly 212 is advanced by the firing rod 58.The drive assembly 212 abuts actuation sled 234 and pushes actuationsled 234 through longitudinal slots 230 of staple cartridge 220 toadvance cam wedges 232 into sequential contact with pushers 228. Pushers228 translate vertically along cam wedges 232 within fastener retentionslots 225 and urge fasteners 226 from retention slots 225 into stapledeforming cavities 206 (FIG. 8) of anvil assembly 24.

The drive assembly 212 includes a drive beam 266 with a working head268. The distal end of working head 268 of drive beam 266 is defined bya vertical support strut 278 (FIG. 9) which supports a knife blade 280,and an abutment surface 283 which engages a portion of actuation sled234 during a stapling procedure. Knife blade 280 is positioned totranslate slightly behind the actuation sled 234 through a centrallongitudinal slot 282 in staple cartridge 220 to form an incisionbetween rows of stapled body tissue. A retention flange 40 projectsdistally from vertical strut 278 and supports a cylindrical cam roller40 a at its distal end. Cam roller 40 a is dimensioned and configured toengage cam surface 42 on anvil portion 28 to clamp anvil portion 28against body tissue.

In use, the user manipulates handle assembly 12 to clamp tissue and firestaples. To approximate the cartridge and anvil assemblies 22 and 24 andclamp tissue, movable handle 28 is moved in the direction towardstationary handle member 26. Movable handle 28 is compressed towardsstationary handle 26 against the bias of torsion spring 42 to engageactuation shaft 52. The engagement finger 62 of pawl 48 engages thetoothed rack 60 of actuation shaft 52 to advance actuation shaft 52 andfiring rod 58 distally.

Firing rod 58 is connected at its distal end to axial drive assembly 212including drive beam 266, such that advancement of firing rod 58 effectsadvancement of drive beam 266. As drive beam 266 is advanced, cam roller40 a moves into engagement with cam surface 42 of anvil portion 28 tourge anvil portion 28 in the direction of the cartridge 220 toapproximate cartridge and anvil assemblies 22 and 24 and clamp tissuetherebetween.

After movable handle 28 is actuated to approximate cartridge and anvilassemblies 22 and 24, biasing member 42 returns handle to itsnon-compressed position spaced from stationary handle 26.

To fire stapling device 10 once tissue is clamped, the movable handle 28is moved toward stationary handle member 26 through an actuation strokeduring which, engagement finger 62 of pawl 48 engages toothed rack 60 ofactuation shaft 52 to further advance actuation shaft 52 and firing rod58 distally. More than one actuation stroke may be required to fire allthe staples from the loading unit 16. As firing rod 58 is advanced inthe manner discussed above, drive beam 266 is advanced distally andengages actuation sled 234 through staple cartridge 22 to simultaneouslysever tissue with knife 280 and drive pushers 228 to sequentially ejectstaples 226 from the cartridge. Loading units having staple lines ofdifferent lengths may be used and the number of actuating strokes willvary accordingly. The structure and operation of the tool assembly maybe in accordance with certain embodiments disclosed in U.S. Pat. No.5,865,361, the disclosure of which is hereby incorporated by referenceherein.

The elongated body 14 is mounted in a rotatable member 32 as shown inFIG. 5 and the rotatable member 32 is attached to the handle assembly 12so as to allow the elongated body 14 and loading unit 16, including thetool assembly 20, to rotate around the longitudinal axis. The rotatablemember 32 is formed from one or more tubular or conical members andhouses an articulation actuation mechanism for articulating the toolassembly 20 with respect to the longitudinal axis of the device 10. Thearticulation actuation mechanism includes an articulation lever 122(FIG. 6). The articulation lever 122 is operably connected to anarticulation arm extending through the elongated body 14. Thearticulation lever 122 may be connected to a mechanism for definingpredetermined degrees of articulation of the tool assembly 20. Theoperation and structure of the articulation lever 122 may be asdescribed in U.S. Published Patent Application No. 2004/0232201, thedisclosure of which is hereby incorporated by reference herein. Thearticulation lever 122 is mounted on the rotatable member 32 about apivot pin and is attached to an articulation arm so that rotation of thelever 122 about the pivot pin effects longitudinal motion of thearticulation arm. The articulation arm extends through the elongatedbody 14 and is attached to an articulation link 256 of the loading unit16 (FIG. 9) when the loading unit 16 is mounted on the elongated body14. The articulation lever 122 can be rotated by the user of thesurgical stapling device 10 to articulate the tool assembly 20. As thearticulation lever 122 is rotated in a first direction, the articulationarm attached to the lever is advanced in the distal direction. Thearticulation arm advances the articulation link 256 of the loading unit16 and pivots the mounting assembly 202 about pivot 244 to articulatethe tool assembly 20 in the first direction. As the articulation lever122 is rotated in a second direction, the articulation arm attached tothe lever is retracted in the proximal direction. The articulation armretracts the articulation link 256 of the loading unit 16 and pivots themounting assembly 202 about pivot 244 to articulate the tool assembly 20in the second direction.

As depicted in FIG. 6, the loading unit 16 is removably mounted on thedistal end of the elongated body 14. The body portion 18 of the loadingunit 16 includes a first housing 250 and a second housing 252 thatdefine a channel 253 for allowing the advancement of the axial driveassembly 212. (FIG. 9). The housings 250 and 252 also define a slot forthe articulation link 256. The housings 250 and 252 are received in anouter tube 251. The proximal ends of the housings 250 and 252 define aninsertion tip 193 on which is formed a pair of lugs 254. The lugs 254form a releasable connection with the elongated body 14 so that theloading unit 16 may be mounted on and removed from the elongated body14. A pair of blowout plates 255 are positioned adjacent the distal endof the proximal body portion 18 and adjacent the mounting assembly 202.The blowout plates 255 support the drive assembly 212 duringarticulation and firing of the tool assembly 20. The structure andoperation of the blowout plates 255 are described more fully in U.S.Published Patent Application No. 2004/0232201, the disclosure of whichis hereby incorporated by reference herein.

The distal end of the elongated body 14 defines a tip assembly 301 formounting the loading unit 16 thereon. FIGS. 10-15 and 18 show a tipassembly 301 according to the present disclosure. The tip assemblyincludes a ring 300 mounted to the distal end of the elongated body 14so that it is rotationally fixed and a yoke 400 movably mounted to thering 300. (See FIGS. 10 and 14). The ring 300 defines a passage 303 inwhich two helical guiding ramps 302 are formed. Each of the guidingramps has a distal end 304 and a proximal end 306 and a ledge 310adjacent the proximal end 306. A groove 312 is defined in the innersurface of the ring 300 for mounting the yoke 400 thereon. (See FIG.10).

The moveable yoke 400 has at least one protrusion for interacting withthe lugs 254 on the loading unit 16. As shown in FIG. 11, theprotrusions include two tabs 402 and two stops 404 arranged in pairs sothat each tab 402 and stop 404 define a receiving space 501. The distalend of the yoke 400 also has a ridge 406 which cooperates with thegroove 312 of the ring 300 so that the yoke 400 is rotatable withrespect to the ring 300 from a first, initial position to a secondposition. As the yoke 400 rotates, the positions of the tabs and stopswith respect to the proximal ends 306 of the guiding ramps 302 change.In the first position of the yoke 400 as shown in FIG. 11, a tab 402 andstop 404 pair are disposed adjacent one of the proximal ends 306 of oneof the guiding ramps 302, so that receiving space 501 is positioned forreceiving one of the lugs 254 of the loading unit 16. In the secondposition of the yoke 400 as shown in FIG. 12, the tab 402 and stop 404pair are positioned so that the receiving space 501, and the lug 254disposed therein, is disposed beneath the ledge 310.

The loading unit 16 is inserted into the tip assembly 301 so that theinsertion tip 193 is inserted into passage 303. The lugs 254 areadvanced into the passage 303 of the ring 300 and contact the distalends 304 of the guiding ramps 302. (See FIG. 11). When the loading unit16 is rotated in Direction A (see FIG. 12), the lugs 254 are guided onthe guiding ramps 302 towards the proximal ends 306 of the guiding ramps302 and drop into the receiving spaces 501 of the yoke 400. FIG. 14shows the lugs 254 in the receiving spaces 501. The tip assembly 301 isstill in the first position and a stop 404 and tab 408 are disposed oneither side of a lug 254, and adjacent a proximal end 306 of one of theguiding ramps 302. In this position, the loading unit 16 may be moveddistally and removed from the elongated body 14. The user continues torotate the loading unit 16 in Direction A, so that lugs 254 push againstthe tabs 402, thereby rotating moveable yoke 400 into the secondposition, as shown in FIG. 12. The lugs 254 are situated beneath ledges310. FIG. 15 shows the lugs 254 positioned beneath ledges 310. The stops404 prevent the loading unit 16 from rotating with respect to the yoke400. Thus, the loading unit 16 is captured in the tip assembly 301 andcannot be moved without rotating the yoke 400.

As the loading unit 16 is mounted on to the distal end of the elongatedbody 14, a distal end of the firing rod 58 is connected to the proximalend of the drive assembly 212. The proximal end of the drive assembly212 includes a drive member 272 with a porthole for receiving the distalend of the firing rod 58. When the loading unit 16 is rotated duringmounting of the loading unit, the articulation link 256 moves intoengagement with engagement structure on the distal end of thearticulation arm.

To remove the loading unit 16 from the device, the loading unit 16 isrotated in the direction opposite to Direction A, rotating the yoke 400with it. The lugs 254 are thereby moved away from the ledges 310. Thearticulation link 256 and the articulation arm are moved away fromengagement with one another as the loading unit is rotated. The loadingunit 16 can be removed from the device by continuing to rotate theloading unit 16 so that the lugs 254 follow the guiding ramps 302 towardthe distal ends 304 and moving the DLU distally. In removing the DLUfrom the elongated body 14, the firing rod 58 is disengaged from thedrive assembly 212.

The surgical stapling device 10 according to the present disclosureincludes a sensor mechanism 510 and a locking structure 513, as shown inFIGS. 16-23. The sensor mechanism 510 and the locking structure 513interact with the tip assembly 301 (FIG. 17) to secure the loading unit16 onto the elongated body 14. The sensor mechanism 510 and lockingstructure 513 release the loading unit 16 from the elongated body 14.The locking structure 513 locks the firing rod 58 in position until theloading unit 16 is loaded onto the elongated body 14.

The sensor mechanism 510 includes a sensor tube 502 having a distal endwith a groove 504, as shown in FIG. 18. The yoke 400 of the tip assembly301 has a protrusion 407 that engages the groove 504 and keys movementof the yoke 400 to the sensor tube 502. As the yoke 400 is rotatedduring the loading of the loading unit 16, the sensor tube 502 isrotated in the same direction. The proximal end of the sensor tube 502is connected to the locking structure 513. The locking structure 513includes a button 514 or other manipulatable actuator at the proximalend of the elongated body 14, or on the handle assembly 12, so that itis accessible to the user of the device 10. For example, the button 514is shown in FIG. 19 on the rotatable member 32. The button 514 has abutton tang 512 that extends toward the sensor tube 502. A releaseflange 508 is attached to the sensor tube 502 and rotates with thesensor tube 502 from a first position away from button tang 512 (FIG.20) to a second position in which movement of the release flange 508 isblocked by button tang 512 of locking structure 513 (FIG. 19). Thebutton 514 is biased in the distal direction by a spring.

A plunger 516 interacts with the firing rod 58. The firing rod 58proximal end 524 has a notch 526 defined therein, as best seen in FIGS.20-23. The plunger 516 has a first end for engaging the firing rod 58 atthe notch 526 and a second end with a beveled surface 522 that ispositioned so as to communicate with the button 514 (FIGS. 21 and 23).The plunger 516 is biased in a direction away from the firing rod 58.

In the initial position, before a loading unit 16 is mounted on thedevice 10, the locking structure 510 engages the firing rod 58 in thenotch 526, preventing the advancement of the firing rod 58. The releaseflange 508 prevents the button 514 from moving distally so that thebutton 514 maintains the plunger 516 in engagement with the notch 526.When the loading unit 16 is mounted onto the device, the yoke 400 isturned, thereby turning the sensor tube 502. The release flange 508moves away from button tang 512, allowing the button 514 to movedistally. The button 514 allows the plunger 516 to move away from notch526, as shown in FIG. 23. The locking structure 510 has been disengagedfrom firing rod 58, allowing the firing rod 58 to move when the moveablehandle 28 is manipulated and the device 10 is actuated to clamp tissueand fire staples. The loading unit 16 is also locked onto the device 10,as the release lever 508 is blocked by the button tang 512, preventingrotation of the sensor tube 502. With the sensor tube 502 prevented fromrotation, the yoke 400, which holds the loading unit 16 onto the device10, is prevented from rotation.

When the loading unit 16 is to be removed from the device 10, button 514of locking structure 510 is moved against the bias of the button spring,as shown in FIG. 21, moving button tang 512 away from release flange508, as shown in FIG. 20. The loading unit 16 can then be rotated andremoved from the tip assembly 301 on the elongated body 14. In addition,the locking structure 510 engages the firing rod 58, as the button 514cams the plunger 516 downwardly into the notch 526, as shown in FIG. 21.

A locking structure and/or sensor mechanism in accordance with thepresent disclosure may be used to secure any surgical loading unit, suchas a staple cartridge, replaceable tool assembly, or other end effector,while providing for the release of the same from a surgical instrument.Desirably, the manipulatable actuator for releasing and/or locking thesurgical loading unit is disposed adjacent the handle assembly. In anendoscopic instrument, the manipulatable actuator is disposed at oradjacent to the proximal end of the endoscopic shaft or elongated body.

After firing and before removing a loading unit, a retraction mechanismis employed. The retraction mechanism includes return knobs 36 (FIG. 1)which are connected to the proximal end of actuation shaft 52 by acoupling rod 82 (FIG. 4). Coupling rod 82 has right and left engagementportions 82 a and 82 b which extend through elongated slots 83 (FIG. 1)formed in housing half-sections 38 a and 38 b and are configured toreceive return knobs 36. A central portion 82 c of coupling rod 82 isdimensioned to be slidably received within slots 84 formed in theproximal end of actuation shaft 52. A release plate 86 is supported onone side of actuation shaft 52 by a pair of pins 88 (FIG. 4). Pins 88are positioned within angled cam slots 90 formed through release plate86. Coupling rod 82 extends through an opening 92 formed in the proximalend of release plate 86.

In use, when knobs 36 are pulled rearwardly by a surgeon, coupling rod82 initially moves release plate 86 rearwardly in relation to actuationshaft 52 as rod 82 slides in slots 84 of actuation shaft 52. As thisoccurs, pins 88 cam release plate 86 downwardly to a position coveringtoothed rack 60 of actuation shaft 52 to disengage finger 62 of pawl 48from toothed rack 60. When coupling rod 82 is pulled rearwardly to aposition at which it engages the back end 84 a of slots 84, additionalrearward movement of knobs 36 effect proximal movement of actuationshaft 52 and firing rod 58.

A hook 96 is supported in a slot 98 formed in a top surface of actuationshaft 52. Hook 96 includes a throughbore 96 a dimensioned to receivecoupling rod 82. A forward end of hook 96 includes an upturned portion98 configured to receive one looped end 100 a of spring 100. Theopposite end of spring 100 includes a loop 100 b dimensioned to receivea post 102 formed on actuation shaft 52. Spring 100 is maintained intension to urge coupling rod 82 towards the forward end of slots 84 inactuation shaft 52. When coupling rod 82 is positioned at the forwardend of slots 84 of actuation shaft 52, release plate 86 is held orcammed in a raised position above toothed rack 60 of actuation shaft 52.

It will be understood that various modifications may be made to theembodiments disclosed herein. For example, the above described lockassembly may be incorporated into a variety of surgical instrumentswhich include loading unit's and is not limited to use on endoscopicstaplers. Further, the loading unit may be configured to receive aninsertion tip of a surgical instrument in contrast to that disclosed.Therefore, the above description should not be construed as limiting,but merely as exemplifications of various embodiments. Those skilled inthe art will envision other modifications within the scope and spirit ofthe claims appended hereto.

1. A surgical instrument comprising: a loading unit having a tool assembly; and an elongated body having a proximal end and a distal end, the distal end of the elongated body including a securing structure for securing the loading unit onto the elongated body, the securing structure including at least one guiding ramp and a moveable yoke with a first position and a second position, the loading unit being secured on the elongated body when the yoke is in the second position; the at least one guiding ramp being arranged to guide movement of the loading unit in a predetermined direction toward engagement with the yoke, the yoke being movable toward the second position as the loading unit is moved in the predetermined direction.
 2. The surgical instrument according to claim 1, wherein the loading unit has a projecting part for engaging the yoke.
 3. The surgical instrument according to claim 1, wherein the at least one guiding ramp defines an arcuate path.
 4. The surgical instrument according to claim 1, wherein the securing structure includes a ring defining a passage, two guiding ramps being defined by the ring and extending in the passage.
 5. The surgical instrument according to claim 4 wherein the guiding ramps are helical in shape.
 6. The surgical instrument according to claim 4 wherein the guiding ramps are disposed approximately 180 degrees apart.
 7. The surgical instrument according to claim 1, wherein each of the at least one guiding ramp extends toward the proximal end of the elongated body.
 8. The surgical instrument according to claim 4, wherein the ring is attached to the distal end of the elongated body and the yoke is movably mounted proximal to the ring.
 9. The surgical instrument according to claim 8, wherein the yoke is rotatably mounted to the ring.
 10. The surgical instrument according to claim 9, wherein the yoke and the ring have an inter-engaging groove and ridge structure for allowing rotation.
 11. The surgical instrument according to claim 2, wherein the yoke has at least one protrusion for engagement by the projecting part.
 12. The surgical instrument according to claim 11, wherein the yoke has a pair of protrusions.
 13. The surgical instrument according to claim 12, wherein the pair of protrusions is disposed adjacent a proximal end of the guiding ramp when the yoke is in the first position.
 14. The surgical instrument according to claim 13, wherein the pair of protrusions defines a receiving space for the projecting part.
 15. The surgical instrument according to claim 2, wherein the securing structure has a ledge and the projecting part is proximal to the ledge when the yoke is in the second position, securing the loading unit onto the elongated body.
 16. A surgical instrument comprising: an elongated body having a proximal end, a distal end, and a rod extending therethrough; and a loading unit removably mountable with the distal end of the elongated body and having a tool assembly; and a sensor mechanism arranged for engagement by the loading unit and movement with the loading unit upon mounting the loading unit on the distal end of the elongated body; a handle assembly including a locking structure having a first position for blocking movement of the sensor mechanism and a second position for allowing movement of the sensor mechanism so that the loading unit is removable from the elongated body when the sensor mechanism is in the second position.
 17. The surgical instrument according to claim 16, wherein the locking structure engages the rod when the locking structure is in the second position.
 18. The surgical instrument according to claim 17, wherein the locking structure has a plunger arranged to engage the rod.
 19. The surgical instrument according to claim 18, wherein the rod has a notch arranged for engagement by the plunger.
 20. The surgical instrument according to claim 16, wherein the locking structure includes a button that is accessible by the user of the surgical instrument.
 21. The surgical instrument according to claim 16, wherein the sensor mechanism includes a sensor tube.
 22. The surgical instrument according to claim 21, wherein the sensor tube is attached to a movable yoke at a distal end of the sensor tube, the movable yoke being arranged for engagement by and movement with the loading unit.
 23. The surgical instrument according to claim 22, wherein the sensor tube is attached to a release flange at a proximal end thereof.
 24. The surgical instrument according to claim 23, wherein the locking structure includes a tang for blocking movement of the release flange when the locking structure is in the first position.
 25. The surgical instrument according to claim 23, wherein the release flange includes a cam surface for camming a plunger into engagement with the rod.
 26. A method of mounting a loading unit onto a surgical instrument, comprising: providing a surgical instrument with a handle assembly and an elongated body, the elongated body having a guiding ramp terminating at a receiving space defined by rotatable securing structure; providing a loading unit with a tool assembly; engaging the loading unit with the guiding ramp on the elongated body of the surgical instrument; rotating the loading unit so that the loading unit follows the guiding ramp and engages the securing structure; and rotating the loading unit into a secured position with respect to the elongated body so that the securing structure rotates with the loading unit; and locking the securing structure when the loading unit is in the secured position.
 27. The method of claim 26, wherein the surgical instrument includes a structure for releasing the securing structure.
 28. A method of removing a loading unit from a surgical instrument, comprising: providing a surgical instrument with a handle assembly and an elongated body, the elongated body defining movable securing structure, the handle assembly having a locking structure with a first position blocking movement of the securing structure and a second position allowing movement of the securing structure; providing a loading unit with a tool assembly, the loading unit being secured on the elongated body by the securing structure; moving the locking structure from the first position to the second position; and removing the loading unit from the surgical instrument.
 29. The method according to claim 28, wherein the loading unit is removed by rotating the loading unit, the loading unit interacting with the securing structure so that the securing structure moves with the loading unit.
 30. The method according to claim 29, wherein the loading unit is moved by rotating the loading unit, the securing structure rotating therewith. 